Gas-phase valence photoelectron spectra are reported for 2,3,7,8,12,13,17,18-octaethylporphyrin (OEPH2) and 5,10,15,20-tetraphenylporphyrin (TPPH2). Comparison of spectra collected with He I and He II sources gives an empirical assignment of the relative order of the low-energy 2Au and 2B1u ion states in the gas phase. For OEPH2, the first ionization at 6.24 eV is assigned to the 2Au ion state, with the 2B1u ionization located 0.25 eV to higher energy. The photoelectron spectrum reported here is quite different from the previously reported spectrum of OEPH2. The first ionization of TPPH2 is assigned to the 2B1u ion state, with the 2Au ionization 0.27 eV to higher energy. The reversal of the ordering of the first two ionizations of OEPH2 and TPPH2 is due to the different site of the substituents and the different nodal properties of the porphyrin Orbitals.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry